Production of adipic acid and derivatives from carbohydrate-containing materials

ABSTRACT

The present invention generally relates to processes for the chemocatalytic conversion of a carbohydrate source to an adipic acid product. The present invention includes processes for the conversion of a carbohydrate source to an adipic acid product via a furanic substrate, such as 2,5-furandicarboxylic acid or derivatives thereof. The present invention also includes processes for producing an adipic acid product comprising the catalytic hydrogenation of a furanic substrate to produce a tetrahydrofuranic substrate and the catalytic hydrodeoxygenation of at least a portion of the tetrahydrofuranic substrate to an adipic acid product. The present invention also includes products produced from adipic acid product and processes for the production thereof from such adipic acid product.

REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. provisional application Ser. No.61/268,414, filed Jun. 13, 2009, the entire disclosure of which isincorporated herein by reference.

FIELD OF THE INVENTION

The present invention generally relates to processes for thechemocatalytic conversion of a carbohydrate source to an adipic acidproduct. The present invention includes processes for the conversion ofa carbohydrate source to an adipic acid product via a furanic substrate,such as 2,5-furandicarboxylic acid or derivatives thereof. The presentinvention also includes processes for producing an adipic acid productcomprising the catalytic hydrogenation of a furanic substrate to producea tetrahydrofuranic substrate and the catalytic hydrodeoxygenation of atleast a portion of the tetrahydrofuranic substrate to an adipic acidproduct. The present invention also relates to processes for thepreparation of industrial chemicals such as adiponitrile, hexamethylenediamine, caprolactam, caprolactone, adipate esters, 1,6-hexanediol,polyamides (e.g., nylons) and polyesters from an adipic acid productobtained from processes including the catalytic hydrodeoxygenation of atetrahydrofuranic substrate. The invention is further directed to suchindustrial chemicals produced from adipic acid product produced by theprocesses of the present invention.

BACKGROUND OF THE INVENTION

For at least the last forty years, experts in the scientific andeconomic communities have been predicting diminishing availability ofpetrochemical resources to produce the energy and chemical-basedmaterials needed throughout the world. Fortunately, for much of thisperiod, newly discovered petroleum reserves, and advances in petroleumproduction and conversion technologies have enabled the supply of theseresources and the products producible therefrom to substantially keeppace with the ever-increasing demands. More recently, however, the rapidrate of industrialization of the world's most populous countries, Chinaand India, coupled with increased political instability inpetroleum-producing regions (most notably the Middle East, Nigeria, andVenezuela), have pushed oil prices to record levels, adversely affectingthe US economy, among others. Moreover, environmental, ecological, andpolitical considerations in the US continue to impact the production ofthis valuable resource by, among other matters, removing proven reservesfrom commercial exploitation.

The combined effects of ever-increasing demand and slowing rates ofincrease in the production of petroleum affect not only gasoline, dieselfuel and heating oil prices but also the prices of the vast array ofchemicals that are feedstock's for an equally vast array of products,from drugs to plastics to pesticides, to name a few.

Over the past decade, this adverse economic impact has become a drivingfactor for developing alternative and sustainable ways to meetchemical-based materials needs. The Roadmap for Biomass Technologies inthe United States (U.S. Department of Energy, Accession No. ADA436527,December 2002), authored by 26 leading experts, predicts that, by 2030,25% of all chemicals consumed in the United States will be produced frombiomass. More recently, the U.S. Department of Energy has identified 12top-tier chemical building blocks from biomass processing, as reportedin the Biomass Report for the DOE Office of Energy Efficiency andRenewable Energy entitled Top Value Added Chemicals from Biomass, Volume1-Results of Screening for Potential Candidates from Sugars andSynthesis Gas, August 2004.

It has been reported that of the approximately 200 billion tons ofbiomass produced per year, 95% of it is in the form of carbohydrates,and only 3 to 4% of the total carbohydrates are currently being used forfood and other purposes. Thus, there is an abundant untapped supply ofbiomass carbohydrates, which can potentially be used for the productionof non-petroleum based specialty and industrial chemicals that are fullyrenewable. That said, biorenewable routes to sustainable supplies ofvaluable chemicals such as, for example, alcohols, aldehydes, ketones,carboxylic acids, and esters useful for producing a vast array ofproducts are less likely to become a reality until the cost ofconverting biomass to these chemicals is more nearly comparable to or,more preferably, advantaged as compared to the corresponding productioncost from petroleum-based feedstocks.

Adipic acid is among the end products producible from biorenewablefeedstocks. Such processes have been disclosed in, for example, U.S.Pat. Nos. 4,400,468 and 5,487,987 and, for example, in “Benzene-FreeSynthesis of Adipic Acid”, Frost et al. Biotechnol. Prog. 2002, Vol. 18,pp. 201-211. However, to date, no process for producing adipic acid frombiorenewable feedstocks has been commercialized.

Among the list of 12 building block chemicals targeted by the USgovernment for production from biomass is 2,5-furandicarboxylic acid,and the government has solicited proposals for the use thereof in theproduction of industrial chemicals. To date, large scale production ofhigh value industrial chemicals from 2,5-furandicarboxylic acid has notbeen achieved.

To that end, applicants have discovered processes which enable theproduction of high value, large market industrial chemicals costeffectively from a key building block material such as2,5-furandicarboxylic acid.

SUMMARY OF THE INVENTION

Briefly, therefore, the present invention is directed to processes forpreparing an adipic acid product from a carbohydrate source comprisingthe steps of converting the carbohydrate source to a furanic substrateand converting at least a portion of the furanic substrate to the adipicacid product. In accordance with various embodiments, processes forproducing an adipic acid product from a furanic substrate are disclosedwhich comprise converting by chemocatalytic means at least a portion ofthe furanic substrate to the adipic acid product. Further, in accordancewith the present invention, processes for producing an adipic acidproduct further comprise converting at least a portion of the furanicsubstrate to a tetrahydrofuranic substrate and converting at least aportion of the tetrahydrofuranic substrate to the adipic acid product.

In accordance with various embodiments, the process for preparing anadipic acid product comprises converting by chemocatalytic means to theadipic acid product a substrate of formula I

or a salt thereof, or an intermolecular homomer or heteromer thereof, orintermolecular or intramolecular anhydrides or stereoisomers thereof,all collectively referred to as “furanic substrate,” wherein each X isindependently selected from the group consisting of —OH, —OR², and —H,or, in some embodiments, X is independently selected from the groupconsisting of —OH and —H, or, in some embodiments, each X is —OH, or, insome embodiments, each X is —H; Y is selected from the group consistingof —C(O)OH, —C(O)OR¹, —C(O)NR³R⁴, and —CH₂NR³R⁴; Z is selected from thegroup consisting of —C(O)OH, —C(O)OR¹, —C(O)NR³R⁴, and —CH₂NR³R⁴; eachR¹ is independently selected from the group consisting of hydrocarbyland substituted hydrocarbyl; each R² is independently selected from thegroup consisting of hydrocarbyl and substituted hydrocarbyl; each R³ isindependently selected from the group consisting of hydrogen,hydrocarbyl, and substituted hydrocarbyl; each R⁴ is independentlyselected from the group consisting of hydrogen, hydrocarbyl, andsubstituted hydrocarbyl; and, preferably, each hydrocarbyl orsubstituted hydrocarbyl in any of the aforementioned R¹, R², R³, and/orR⁴ can be independently selected from the group consisting of alkyl,alkylene, alkoxy, alkylamino, thioalkyl, haloalkyl, cycloalkyl,cycloalkylalkyl, heterocyclyl, N-heterocyclyl, heterocyclylalkyl, aryl,aralkyl heteroaryl, N-heteroaryl and heteroarylalkyl, in each caseoptionally substituted.

In various embodiments, the present invention is directed to processesfor preparing an adipic acid product comprising reacting atetrahydrofuranic substrate with hydrogen, in the presence of ahydrodeoxygenation catalyst, a solvent and a source of halogen, toconvert at least a portion of the tetrahydrofuranic substrate to theadipic acid product, wherein the tetrahydrofuranic substrate is acompound of formula III (and salts thereof),

wherein each X is independently selected from the group consisting of—OH, —OR², and —H, or, in some embodiments, X is independently selectedfrom the group consisting of —OH and —H, or, in some embodiments, each Xis —OH, or, in some embodiments, each X is —H; Y is selected from thegroup consisting of —C(O)OH, —C(O)OR¹, —C(O)NR³R⁴, and —CH₂NR³R⁴; Z isselected from the group consisting of —C(O)OH, —C(O)OR¹, —C(O)NR³R⁴, and—CH₂NR³R⁴; each R¹ is independently selected from the group consistingof hydrocarbyl, and substituted hydrocarbyl; each R² is independentlyselected from the group consisting of hydrocarbyl and substitutedhydrocarbyl; each R³ is independently selected from the group consistingof hydrogen, hydrocarbyl, and substituted hydrocarbyl; each R⁴ isindependently selected from the group consisting of hydrogen,hydrocarbyl, and substituted hydrocarbyl; and, preferably, eachhydrocarbyl or substituted hydrocarbyl in any of the aforementioned R¹,R², R³, and/or R⁴ can be independently selected from the groupconsisting of alkyl, alkylene, alkoxy, alkylamino, thioalkyl, haloalkyl,cycloalkyl, cycloalkylalkyl, heterocyclyl, N-heterocyclyl,heterocyclylalkyl, aryl, aralkyl heteroaryl, N-heteroaryl andheteroarylalkyl, in each case optionally substituted.

The present invention is further directed to processes for preparingadipic acid or derivative thereof by reacting a tetrahydrofuranicsubstrate comprising tetrahydrofuran-2,5-dicarboxylic acid (THFDCA) withhydrogen in the presence of hydrogen iodide or hydrogen bromide and asolvent, wherein at least a portion of thetetrahydrofuran-2,5-dicarboxylic acid is converted to adipic acid orderivative thereof.

The present invention is further directed to processes for preparingadipic acid or derivative thereof comprising reacting a furanicsubstrate with hydrogen, in the presence of a hydrogenation catalyst anda solvent, but in the absence of an added source of halogen, to convertat least a portion thereof to a tetrahydrofuranic substrate, andreacting at least a portion of the tetrahydrofuranic substrate withhydrogen, in the presence of a hydrodeoxygenation catalyst, a solventand an added source of halogen, to convert at least a portion of thetetrahydrofuranic substrate to adipic acid or derivative thereof.

In various embodiments of the present invention, processes for preparingadipic acid product comprise reacting a furanic substrate with hydrogen,in the presence of a hydrogenation catalyst and acetic acid, but in theabsence of an added source of halogen, to convert at least a portionthereof to a tetrahydrofuran-2,5-dicarboxylic acid and reacting at leasta portion of the tetrahydrofuran-2,5-dicarboxylic acid with hydrogen, inthe presence of a hydrodeoxygenation catalyst, solvent and hydrogeniodide or hydrogen bromide, to convert at least a portion of thetetrahydrofuran-2,5-dicarboxylic acid to an adipic acid productcomprising adipic acid.

The present invention is further directed to processes for thepreparation of industrial chemicals such as adiponitrile, hexamethylenediamine, caprolactam, caprolactone, adipate esters, 1,6-hexanediol,polyamides (e.g., nylons) and polyesters from an adipic acid productobtained from processes for the chemocatalytic conversion of acarbohydrate source, which processes typically include the catalytichydrodeoxygenation of a tetrahydrofuranic substrate.

The present invention is further directed to processes for thepreparation of industrial chemicals such as adiponitrile, hexamethylenediamine, caprolactam, caprolactone, 1,6-hexanediol and polyamides (e.g.,nylons) from an adipic acid product obtained from processes for thechemocatalytic conversion of a carbohydrate source, which processesinclude the catalytic hydrogenation of a furanic substrate and thecatalytic hydrodeoxygenation of a tetrahydrofuranic substrate.

The present invention is further directed to adipic acid product,polyamides, polyesters and caprolactam produced at least in part fromadipic acid product produced by processes comprising the chemocatalyticconversion of a tetrahydrofuranic substrate, and, more particularly, atetrahydrofuranic substrate comprising tetrahydrofuran-2,5-dicarboxylicacid or derivative thereof into an adipic acid product.

The present invention is further directed to adipic acid product,polyamides, polyesters and caprolactam produced at least in part fromadipic acid product produced by processes comprising the catalytichydrogenation of a furanic substrate and the catalytichydrodeoxygenation of a tetrahydrofuranic substrate.

Other objects and features will become apparent and/or will be pointedout hereinafter.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

I. Source Materials

Biorenewable sources such as corn grain (maize), sugar beet, sugar caneas well as energy crops, plant biomass, agricultural wastes, forestryresidues, sugar processing residues, plant-derived household wastes,municipal waste, spent paper, switch grass, miscanthus, cassaya, trees(hardwood and softwood), vegetation, crop residues (e.g., bagasse andcorn stover) are all rich in hexoses, which can be used to produce furanderivatives, such as 5-hydroxymethylfurfural (HMF). Hexoses are readilyproduced from such carbohydrate sources by hydrolysis. It is alsogenerally known that biomass carbohydrates can be enzymaticallyconverted to glucose, fructose and other sugars. Dehydration of fructosecan readily produce furan derivatives such as HMF. Acid hydrolysis ofglucose is also known to produce HMF; see, for example, U.S. Pat. No.6,518,440. Various other methods have been developed for producing HMFincluding, for example, those described in U.S. Pat. No. 4,533,743 (toMedeiros et al.), U.S. Pat. No. 4,912,237 (to Zeitsch), U.S. Pat. No.4,971,657 (to Avignon et al.), U.S. Pat. No. 6,743,928 (to Zeitsch),U.S. Pat. No. 2,750,394 (to Peniston), U.S. Pat. No. 2,917,520 (toCope); U.S. Pat. No. 2,929,823 (to Garber), U.S. Pat. No. 3,118,912 (toSmith), U.S. Pat. No. 4,339,387 (to Fleche et al.), U.S. Pat. No.4,590,283 (to Gaset et al.), and U.S. Pat. No. 4,740,605 (to Rapp). Inthe foreign patent literature, see GB 591,858, GB 600,871; and GB876,463, all of which were published in English. See also, FR 2,663,933,FR 2,664,273, FR 2,669,635, and CA 2,097,812, all of which werepublished in French. Thus, a variety of carbohydrate sources can be usedto produce HMF by a variety of known techniques.

HMF can be converted to 2,5-furandicarboxylic acid (FDCA) by selectiveoxidation. Examples of processes for the production of FDCA from HMF aredisclosed in, for example, U.S. Pat. Nos. 3,326,944 and 4,977,283, U.S.Pat. App. 2008/0103318, and Japanese Laid-open Application No.H02-088569. See also, Corma et al., ChemSusChem., 2009, p 1138.Derivatives of FDCA can also be produced from HMF by processes such asthose illustrated in Moreau, Topics in Catalysis 2004, Vol. 27, pp. 11;Lewkowski, Arkivoc, 2001 (i), p. 17; Lichtenthaler, C. R., Chimie, Vol.7, p. 65; Moore, Organic Preparations and Procedures International, Vol.4, 1972, p. 289; and also in U.S. Pat. Nos. 3,225,066, 7,579,490 and7,432,382.

Thus, it is known in the art to produce from carbohydrates a variety offurans and derivatives thereof which applicants have discovered areuseful to produce adipic acid product by the processes of the presentinvention.

II. Furanic Substrate and Hydrogenation Thereof

Applicants have discovered that an adipic acid product of formula II,below, can be produced from a carbohydrate source by processes whichcomprise converting by chemocatalytic means a substrate of formula I,below, or a salt thereof, or an intermolecular homomer or heteromerthereof, or intermolecular and intramolecular anhydrides orstereoisomers thereof, hereinafter all collectively referred to as“furanic substrate”, derivable by means known in the art, in accordancewith the following overall reaction

wherein each X is independently selected from the group consisting of—OH, —OR², and —H or, in some embodiments, X is independently selectedfrom the group consisting of —OH and —H, or in some embodiments, each Xis —OH, or, in some embodiments, each X is —H; Y is selected from thegroup consisting of —C(O)OH, —C(O)OR¹, —C(O)NR³R⁴, and —CH₂NR³R⁴; Z isselected from the group consisting of —C(O)OH, —C(O)OR¹, —C(O)NR³R⁴, and—CH₂NR³R⁴; each R¹ is independently selected from the group consistingof hydrocarbyl, and substituted hydrocarbyl; each R² is independentlyselected from the group consisting of hydrocarbyl and substitutedhydrocarbyl; each R³ is independently selected from the group consistingof hydrogen, hydrocarbyl, and substituted hydrocarbyl; each R⁴ isindependently selected from the group consisting of hydrogen,hydrocarbyl, and substituted hydrocarbyl; and, preferably, eachhydrocarbyl or substituted hydrocarbyl in any of the aforementioned R¹,R², R³, and/or R⁴ can be independently selected from the groupconsisting of alkyl, alkylene, alkoxy, alkylamino, thioalkyl, haloalkyl,cycloalkyl, cycloalkylalkyl, heterocyclyl, N-heterocyclyl,heterocyclylalkyl, aryl, aralkyl heteroaryl, N-heteroaryl andheteroarylalkyl, in each case optionally substituted. If substituted,the aforementioned R¹, R², R³, and/or R⁴ can be preferably substitutedwith one or more of C₁-C₄ alkyl, hydroxyl, amine, C₁-C₄ alkylamino,thiol, and C₁-C₄ thioalkyl.

In accordance with the present invention, the furanic substrate isinitially reacted with hydrogen in the presence of a hydrogenationcatalyst to convert at least a portion of the furanic substrate to atetrahydrofuranic substrate, and at least a portion of thetetrahydrofuranic substrate is converted to adipic acid product.

The hydrogenation reaction is typically conducted under conditions knownin the art. See for example, “Catalytic Hydrogenation andDehydrogenation” in Fine Chemicals Through Heterogeneous Catalysis, 2nded., Sheldon and van Bekkum, p. 351; See also Handbook of HeterogeneousCatalytic Hydrogenation for Organic Synthesis, Nishimura 2001 Wiley, NewYork. For example, the hydrogenation reaction is conducted in thepresence of a solvent to the furanic substrate. Solvents suitable forthe hydrogenation reaction include water, alcohols, esters, ethers,ketones, weak carboxylic acids and mixtures thereof. The term “weakcarboxylic acid” as used herein means any unsubstituted or substitutedcarboxylic acid having a pKa of at least about 3.5, more preferably atleast about 4.5 and, more particularly, is selected from amongunsubstituted acids such as acetic acid, propionic acid or butyric acid,or mixtures thereof. Among the useful solvents, acetic acid is morepreferred because it also is useful as a solvent in the subsequenthydrodeoxygenation of the tetrahydrofuranic substrate.

Generally, the temperature of the hydrogenation reaction is at leastabout 30° C., more typically 60° C., or higher. In various embodiments,the temperature of the hydrogenation reaction is from about 60° C. toabout 200° C., and more preferably from about 60° C. to about 160° C.

Typically, the partial pressure of hydrogen is at least about 50 poundsper square inch absolute (psia) (345 kPa), at least about 100 psia (689kPa), at least about 250 psia (1724 kPa), or at least about 500 psia(3447 kPa). In various embodiments, the partial pressure of hydrogen isup to about 2000 psia (13790 kPa), or more typically in the range offrom about 500 psia (3447 kPa) to about 2000 psia (13790 kPa) and stillmore typically in the range of about 1000 psia (6890 kPa) to about 2000psia (13790 kPa).

In general, the hydrogenation reaction can be conducted in a batch,semi-batch, or continuous reactor design using fixed bed reactors,trickle bed reactors, slurry phase reactors, moving bed reactors, or anyother design that allows for heterogeneous catalytic reactions. Examplesof reactors can be seen in Chemical Process Equipment—Selection andDesign, Couper et al., Elsevier 1990, which is incorporated herein byreference. It should be understood that the furanic substrate, hydrogen,any solvent, and the hydrodeoxygenation catalyst may be introduced intoa suitable reactor separately or in various combinations.

Catalysts suitable for the hydrogenation reaction (hydrogenationcatalysts) include heterogeneous catalysts, including solid-phasecatalysts comprising one or more supported or unsupported metals.Suitable catalysts are disclosed in “Catalytic Hydrogenation andDehydrogenation,” Fine Chemicals Through Heterogeneous Catalysis, 2nded., Sheldon and van Bekkum, p. 351 and Handbook of HeterogeneousCatalytic Hydrogenation for Organic Synthesis, Nishimura 2001 Wiley, NewYork. In various embodiments, metal is present at a surface of a support(i.e., at one or more surfaces, external or internal). Typically, metalcomprises at least one d-block metal (i.e., transition metal; groups3-12 of the periodic table). In more preferred embodiments, the metal isselected from the group consisting of palladium, platinum, rhodium,ruthenium, nickel, cobalt, iron and combinations thereof. Additionalother metals may be present, including one or more d-block metals, aloneor in combination with one or more rare earth metals (e.g. lanthanides),alone or in combination with one or more main group metals (e.g. Al, Ga,Tl, In, Sn, Pb or Bi). In general, the metals may be present in variousforms (e.g., elemental, metal oxide, metal hydroxides, metal ions,etc.). Typically, the metal(s) at a surface of a support may constitutefrom about 0.25% to about 10%, or from about 1% to about 8%, or fromabout 2.5% to about 7.5% (e.g., 5%) of the total weight of the catalyst.

In various embodiments, the hydrogenation catalyst comprises a firstmetal (M1) and a second metal (M2) at a surface of a support, whereinthe M1 metal is selected from the group consisting of ruthenium, rhodiumpalladium, platinum, nickel, cobalt and iron and the M2 metal isselected from the group consisting of d-block metals, rare earth metals,and main group metals, wherein the M1 metal is not the same metal as theM2 metal. In various embodiments, M2 is selected from the groupconsisting of molybdenum, ruthenium, rhodium, palladium, iridium,platinum and gold. In various preferred embodiments, the M1 metal ispalladium and the M2 metal is selected from the group consisting ofmanganese, iron, and cobalt.

The M1:M2 molar ratio may vary, for example, from about 500:1 to about1:1, from about 250:1 to about 1:1, from about 100:1 to about 1:1, fromabout 50:1 to about 1:1, from about 20:1 to about 1:1, or from about10:1 to about 1:1. In various other embodiments, the M1:M2 molar ratiomay vary, for example, from about 1:100 to about 1:1, from about 1:50 toabout 1:1, from about 1:10 to about 1:1, from about 1:5 to about 1:1, orfrom about 1:2 to about 1:1.

Moreover, the weight percents of M1 and M2 relative to the catalystweight may vary. Typically, the weight percent of M1 may range fromabout 0.5% to about 10%, more preferably from about 1% to about 8%, andstill more preferably from about 2.5% to about 7.5% (e.g., about 5%).The weight percent of M2 may range from about 0.25% to about 10%, fromabout 0.5% to about 8%, or from about 0.5% to about 5%.

In various other embodiments, a third metal (M3) may be added to producea M1/M2/M3 catalyst wherein the M3 metal is not the same metal as the M1metal and the M2 metal. In yet other embodiments a fourth metal (M4) maybe added to produce a M1/M2/M3/M4 catalyst wherein the M4 metal is notthe same metal as the M1 metal, the M2 metal or the M3 metal. M3 and M4may each be selected from the group consisting of d-block metals, rareearth metals (e.g. lanthanides), or main group metals (e.g. Al, Ga, Tl,In, Sn, Pb or Bi).

Suitable catalyst supports include carbon, alumina, silica, ceria,titania, zirconia, niobia, zeolite, magnesia, clays, iron oxide, siliconcarbide, aluminosilicates, and modifications, mixtures or combinationsthereof. The support materials may be modified using methods known inthe art such as heat treatment, acid treatment or by the introduction ofa dopant (for example, metal-doped titanias, metal-doped zirconias(e.g., tungstated-zirconia), metal-doped cerias, and metal-modifiedniobias). Particularly preferred supports are carbon (which may beactivated carbon, carbon black, coke or charcoal), alumina, zirconia,titania, zeolite and silica. In various embodiments, the support of theoxidation catalyst is selected from the group consisting of carbon,zirconia, zeolite, and silica.

When a catalyst support is used, the metals may be deposited usingprocedures known in the art including, but not limited to incipientwetness, ion-exchange, deposition-precipitation, and vacuumimpregnation. When two or more metals are deposited on the same support,they may be deposited sequentially or simultaneously. In variousembodiments, following metal deposition, the catalyst is dried at atemperature of at least about 50° C., more typically at least about 120°C. for a period of time of at least about 1 hour, more typically 3 hoursor more. In these and other embodiments, the catalyst is dried undersub-atmospheric pressure conditions. In various embodiments, thecatalyst is reduced after drying (e.g., by flowing 5% H₂ in N₂ at 350°C. for 3 hours). Still further, in these and other embodiments, thecatalyst is calcined, for example, at a temperature of at least about500° C. for a period of time (e.g., at least about 3 hours).

The hydrogenation reaction is preferably conducted in the substantialabsence of added halogen. It is currently believed that the introductionof a source of halogen independent of that which, if any, is within thefuranic substrate inhibits the conversion rate and selectivity of thereaction to tetrahydrofuranic substrate.

The reaction product of the hydrogenation step is a tetrahydrofuranicsubstrate, which substrate is unexpectedly convertible to an adipic acidproduct in high yield. The tetrahydrofuranic substrate of the presentinvention is set forth in formula III, below (and further includes saltsthereof):

wherein each X is independently selected from the group consisting of—OH, —OR², and —H, or, in some embodiments, X is independently selectedfrom the group consisting of —OH and —H, or, in some embodiments, each Xis —OH, or, in some embodiments, each X is —H; Y is selected from thegroup consisting of —C(O)OH, —C(O)OR¹, —C(O)NR³R⁴, and —CH₂NR³R⁴; Z isselected from the group consisting of —C(O)OH, —C(O)OR¹, —C(O)NR³R⁴, and—CH₂NR³R⁴; each R¹ is independently selected from the group consistingof hydrocarbyl, and substituted hydrocarbyl; each R² is independentlyselected from the group consisting of hydrocarbyl and substitutedhydrocarbyl; each R³ is independently selected from the group consistingof hydrogen, hydrocarbyl, and substituted hydrocarbyl; each R⁴ isindependently selected from the group consisting of hydrogen,hydrocarbyl, and substituted hydrocarbyl; and, preferably, eachhydrocarbyl or substituted hydrocarbyl in any of the aforementioned R¹,R², R³, and/or R⁴ can be independently selected from the groupconsisting of alkyl, alkylene, alkoxy, alkylamino, thioalkyl, haloalkyl,cycloalkyl, cycloalkylalkyl, heterocyclyl, N-heterocyclyl,heterocyclylalkyl, aryl, aralkyl heteroaryl, N-heteroaryl andheteroarylalkyl, in each case optionally substituted. If substituted,the aforementioned R¹, R², R³, and/or R⁴ can be preferably substitutedwith one or more of C₁-C₄ alkyl, hydroxyl, amine, C₁-C₄ alkylamino,thiol, and C₁-C₄ thioalkyl.

As used throughout this disclosure, the term “hydrocarbyl” refers tohydrocarbyl moieties, preferably containing 1 to about 50 carbon atoms,preferably 1 to about 30 carbon atoms, and even more preferably 1 toabout 18 carbon atoms, including branched or unbranched, and saturatedor unsaturated species. Preferred hydrocarbyl can be selected from thegroup consisting of alkyl, alkylene, alkoxy, alkylamino, thioalkyl,haloalkyl, cycloalkyl, cycloalkylalkyl, heterocyclyl, N-heterocyclyl,heterocyclylalkyl, aryl, aralkyl heteroaryl, N-heteroaryl,heteroarylalkyl, and the like. A hydrocarbyl may be optionallysubstituted hydrocarbyl. Hence, various hydrocarbyls can be furtherselected from substituted alkyl, substituted cycloalkyl and the like.

III. Conversion of Tetrahydrofuranic Substrate to Adipic Acid Product

In accordance with the present invention, an adipic acid product isproduced by processes comprising the step of hydrodeoxygenating atetrahydrofuranic substrate by reacting the same with hydrogen in thepresence of a hydrodeoxygenation catalyst (i.e., catalyst suitable forthe step of hydrodeoxygenation), an added source of halogen and asolvent, to convert at least a portion of the tetrahydrofuranicsubstrate to an adipic acid product.

In various embodiments, the tetrahydrofuranic substrate comprisesTHFDCA, and a portion of the acid is converted by hydrodeoxygenation toan adipic acid product comprising adipic acid.

Without being bound by theory, it is believed that during this reactionTHFDCA is ring opened and halogenated in the presence of the halogensource to produce a ring opened halogenated intermediate containing acarbon-halogen bond. The carbon-halogen bond of the halogenatedintermediate is believed to be converted to a carbon-hydrogen bond viaone or more of the following pathways. In a first pathway, thehalogenated intermediate reacts with hydrogen in the presence of thehydrodeoxygenation catalyst leading to the formation of acarbon-hydrogen bond along with the generation of hydrohalic acid. In asecond pathway, the halogenated intermediate undergoes adehydrohalogenation reaction to form an olefin intermediate andhydrohalic acid. The olefin is further reduced in the presence of thehydrodeoxygenation catalyst leading to the formation of acarbon-hydrogen bond. Effecting the reaction pursuant to the abovedescribed first and second pathways generates hydrohalic acid as aby-product, which is available for further reaction. In a third pathway,the halogenated intermediate reacts with hydrohalic acid leading to theformation of a carbon-hydrogen bond along with the formation ofmolecular halogen (or interhalogen). Effecting the reaction pursuant tothe third pathway generates molecular halogen as a by-product, which isavailable for further reaction. One or more of the various pathwaysdescribed above may occur concurrently.

The halogen source may be in a form selected from the group consistingof atomic, ionic, molecular and mixtures thereof. In variousembodiments, the halogen source is hydrohalic acid. Preferred halogensources include HBr and HI and mixtures thereof. Unexpectedly, HI hasenabled the conversion of greater than 90% of THFDCA to adipic acidproduct.

Generally, the molar ratio of halogen source to the tetrahydrofuranicsubstrate is equal to or less than about 1. Typically, the mole ratio ofthe halogen source to the substrate is from about 0.9:1 to about 0.1:1,more typically from about 0.7:1 to about 0.3:1, and still more typicallyabout 0.5:1.

Generally, the reaction allows for recovery of the halogen source andcatalytic quantities (where molar ratio of halogen to thehydrodeoxygenation substrate is less than about 1) of halogen can beused, recovered and recycled for continued use as a halogen source.

Generally, the temperature of the hydrodeoxygenation reaction of thefuranic substrate is at least about 20° C., typically at least about 80°C., and more typically at least about 100° C. In various embodiments,the temperature of the hydrodeoxygenation reaction is conducted in therange of from about 20° C. to about 250° C., from about 80° C. to about200° C., more preferably from about 120° C. to about 180° C., and stillmore preferably from about 140° C. to about 180° C.

Typically, in the hydrodeoxygenation reaction, the partial pressure ofhydrogen is at least about 25 psia (172 kPa), more typically at leastabout 200 psia (1379 kPa) or at least about 400 psia (2758 kPa). Invarious embodiments, the partial pressure of hydrogen is from about 25psia (172 kPa) to about 2500 psia (17237 kPa), from about 200 psia (1379kPa) to about 2000 psia (13790 kPa), or from about 400 psia (2758 kPa)to about 1500 psia (10343 kPa).

The hydrodeoxygenation reaction is typically conducted in the presenceof a solvent. Solvents suitable for the selective hydrodeoxygenationreaction include water and carboxylic acids, amides, esters, lactones,sulfoxides, sulfones and mixtures thereof. Preferred solvents includewater, mixtures of water and weak carboxylic acid, and weak carboxylicacid. A preferred weak carboxylic acid is acetic acid.

Hydrodeoxygenation of the tetrahydrofuranic substrate can be conductedin a batch, semi-batch, or continuous reactor design using fixed bedreactors, trickle bed reactors, slurry phase reactors, moving bedreactors, or any other design that allows for heterogeneous catalyticreactions. Examples of reactors can be seen in Chemical ProcessEquipment—Selection and Design, Couper et al., Elsevier 1990, which isincorporated herein by reference. It should be understood that thehydrodeoxygenation substrate, halogen source, hydrogen, any solvent, andthe hydrodeoxygenation catalyst may be introduced into a suitablereactor separately or in various combinations.

In various embodiments, the hydrogenation and hydrodeoxygenationreactions can be conducted in the same reactor, particularly when thesolvent for each reaction is the same and a catalyst effective both as acatalyst for hydrogenation and hydrodeoxygenation reactions is employed.In such embodiments, it will be apparent to those skilled in the artthat many of the reactors above disclosed are typically capable of beingoperated under a variety of conditions and can be readily controlled inorder to optimize reaction conditions for the desired conversion ofreactants. Methods for determining optimized conversion conditions caninclude, for example, periodic sampling of the reaction mixture viaknown reactor off-take mechanisms, analysis of the sampled product andcontrol of the process conditions in response thereto. Further, in suchembodiments, the source of halogen is, most preferably, added to thereactor after the hydrogenation reaction has been conducted underprocess conditions sufficient to convert a suitable portion of thefuranic substrate to the tetrahydrofuranic substrate.

In more preferred embodiments, the hydrogenation and hydrodeoxygenationreactions can be conducted in separate reactors, wherein the solvent foreach reaction is the same and the product from the hydrogenationreaction is passed directly into the hydrodeoxygenation reactor. In suchembodiments, it will be apparent to those skilled in the art that manyof the reactors above disclosed are typically capable of being operatedunder a variety of conditions and can be readily controlled in order tooptimize reaction conditions for the desired conversion of reactants.

In more preferred embodiments, the hydrodeoxygenation catalysts areheterogeneous, but a suitable homogeneous catalyst may be employed. Inthese and various other preferred embodiments, the hydrodeoxygenationcatalyst comprises a solid-phase heterogeneous catalyst in which one ormore metals is present at a surface of a support (i.e., at one or moresurfaces, external or internal). Preferred metals are d-block metalswhich may be used alone, in combination with each other, in combinationwith one or more rare earth metals (e.g. lanthanides), and incombination with one or more main group metals (e.g., Al, Ga, Tl, In,Sn, Pb or Bi). Preferred d-block metals are selected from the groupconsisting of cobalt, nickel, ruthenium, rhodium, palladium, osmium,iridium, platinum and combinations thereof. More preferred d-blockmetals are selected from the group consisting of ruthenium, rhodium,palladium, platinum, and combinations thereof. In general, the metalsmay be present in various forms (e.g., elemental, metal oxide, metalhydroxides, metal ions etc.). Typically, the metal(s) at a surface of asupport may constitute from about 0.25% to about 10%, or from about 1%to about 8%, or from about 2.5% to about 7.5% (e.g., 5%) of the catalystweight.

In various embodiments, the hydrodeoxygenation catalyst comprises two ormore metals. For example, two of more metals (M1 and M2) may beco-supported on or within the same support (e.g., as a mixed-metalcatalyst on silica; M1/M2/Silica catalyst), or they may be supported ondifferent support materials. In various embodiments thehydrodeoxygenation catalyst comprises a first metal (M1) and a secondmetal (M2) at a surface of a support, wherein the M1 metal comprises ad-block metal and the M2 metal is selected from the group consisting ofd-block metals, rare earth metals, and main group metals, wherein the M1metal is not the same metal as the M2 metal. In various embodiments, theM1 metal is selected from the group consisting of cobalt, nickel,ruthenium, rhodium, palladium, osmium, iridium, and platinum. In morepreferred embodiments, the M1 metal is selected from the groupconsisting of ruthenium, rhodium, palladium, and platinum. In variousembodiments, the M2 metal is selected from the group consisting oftitanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper,molybdenum, ruthenium, rhodium, palladium, silver, tungsten, iridium,platinum, and gold. In more preferred embodiments, the M2 metal isselected from the group consisting of molybdenum, ruthenium, rhodium,palladium, iridium, platinum, and gold.

In more preferred embodiments, the M1 metal of the hydrodeoxygenationcatalyst is selected from the group of platinum, rhodium and palladium,and the M2 metal is selected from the group consisting of ruthenium,rhodium, palladium, platinum, and gold.

In various embodiments, the M1:M2 molar ratio of the hydrodeoxygenationcatalyst may vary, for example, from about 500:1 to about 1:1, fromabout 250:1 to about 1:1, from about 100:1 to about 1:1, from about 50:1to about 1:1, from about 20:1 to about 1:1, or from about 10:1 to about1:1. In various other embodiments, the M1:M2 molar ratio may vary, forexample, from about 1:100 to about 1:1, from about 1:50 to about 1:1,from about 1:10 to about 1:1, from about 1:5 to about 1:1, or from about1:2 to about 1:1.

Moreover, in various embodiments, the weight percents of M1 and M2 ofthe hydrodeoxygenation catalyst relative to the total catalyst weightmay vary. Typically, the weight percent of M1 may range from about 0.5%to about 10%, more preferably from about 1% to about 8%, and still morepreferably from about 2.5% to about 7.5% (e.g., about 5%). The weightpercent of M2 may range from about 0.25% to about 10%, from about 0.5%to about 8%, or from about 0.5% to about 5%.

In various other embodiments, a third metal (M3) may be added to producea M1/M2/M3 hydrodeoxygenation catalyst wherein the M3 metal is not thesame metal as the M1 metal and the M2 metal. In other embodiments afourth metal (M4) may be added to produce a M1/M2/M3/M4hydrodeoxygenation catalyst wherein the M4 metal is not the same metalas the M1 metal, the M2 metal or the M3 metal. M3 and M4 may each beselected from the group consisting of d-block metals, rare earth metals(e.g. lanthanides), or main group metals (e.g. Al, Ga, Tl, In, Sn, Pb orBi).

Preferred hydrodeoxygenation catalyst supports include carbon, alumina,silica, ceria, titania, zirconia, niobia, zeolite, magnesia, clays, ironoxide, silicon carbide, aluminosilicates, and modifications, mixtures orcombinations thereof. The supports may be modified through methods knownin the art such as heat treatment, acid treatment, the introduction of adopant (for example, metal-doped titanias, metal-doped zirconias (e.g.tungstated zirconia), metal-doped cerias, and metal-modified niobias).In various preferred embodiments, the hydrodeoxygenation catalystsupport is selected from the group consisting of carbon, silica,zirconia and titania.

When a catalyst support is used for the hydrodeoxygenation catalyst, themetals may be deposited using procedures known in the art including, butnot limited to incipient wetness, ion-exchange, deposition-precipitationand vacuum impregnation. When the two or more metals are deposited onthe same support, they may be deposited sequentially, or simultaneously.In various embodiments, following metal deposition, thehydrodeoxygenation catalyst is dried at a temperature of at least about50° C., more typically at least about 120° C. or more for a period oftime of at least about 1 hour, more typically at least about 3 hours ormore. In these and other embodiments, the catalyst is dried undersub-atmospheric conditions. In various embodiments, thehydrodeoxygenation catalyst is reduced after drying (e.g., by flowing 5%H₂ in N₂ at 350° C. for 3 hours). Still further, in these and otherembodiments, the hydrodeoxygenation catalyst is calcined, for example,at a temperature of at least about 500° C. for a period of time (e.g.,at least about 3 hours).

As should be apparent from the disclosure herein, in certain preferredembodiments, the hydrodeoxygenation catalysts useful for thehydrodeoxygenation of the tetrahydrofuranic substrate are also effectiveas catalysts for the hydrogenation of the furanic substrate.

Without being bound by theory not expressly recited in the claims,catalysts mixtures (co-catalysts or mixed metal catalysts) containingmore than one metal may affect separate steps of the mechanisticreaction pathway.

Surprisingly, the production of adipic acid product from thetetrahydrofuranic substrate is quite facile. Yields of adipic acidproduct from the hydrodeoxygenation of this substrate can be at leastabout 90%, or more.

Adipic acid product produced in accordance with the processes of thepresent invention may be recovered from the hydrodeoxygenation reactionby, for example, one or more combinations of conventional methods knownin the art such as, for example, separation of the reaction liquids fromcatalyst (typically a solid) and the halogen (as, for example, vaporphase separation thereof), followed by solvent extraction/evaporation oradipic acid product crystallization.

IV. Downstream Chemical Products

Various methods are known in the art for conversion of adipic acid todownstream chemical products or intermediates including adipate esters,polyesters, adiponitrile, hexamethylene diamine (HMDA), caprolactam,caprolactone, 1,6-hexanediol, aminocaproic acid, and polyamide such asnylons. For conversions from adipic acid, see for example, withoutlimitation, U.S. Pat. Nos. 3,671,566, 3,917,707, 4,767,856, 5,900,511,5,986,127, 6,008,418, 6,087,296, 6,147,208, 6,462,220, 6,521,779,6,569,802, and Musser, “Adipic Acid” in Ullmann's Encyclopedia ofIndustrial Chemistry, Wiley-VCH, Weinheim, 2005.

In accordance with one aspect of the invention, when acetic acid isemployed as a solvent in at least the hydrodeoxygenation of thetetrahydrofuranic substrate, the adipic acid product resulting therefromwill comprise at least one acyl-group-containing compound and, possibly,one or more diacyl compounds; i.e., when Y or Z=—CH₂NR³R⁴ wherein R³ andR⁴ is H, then one or more H atoms will likely be converted to —C(O)Me(acyl group), for example N,N′-diacetyl hexamethylenediamine. In suchaspect of the invention, the acyl group(s) of such compounds can readilybe hydrolyzed (for example, in the presence of a base), wherein they arereconverted to an —H, and the acetic acid can then be regenerated. Thus,hexamethylenediamine (HDMA) can be produced.

In various embodiments, an adipic acid product is converted toadiponitrile wherein the adipic acid product is prepared in accordancewith the present invention. Adiponitrile can be used industrially forthe manufacture of hexamethylenediamine, see Smiley,“Hexamethylenediamine” in Ullmann's Encyclopedia of IndustrialChemistry, Wiley-VCH 2009. Therefore, in further embodiments, an adipicacid product is converted to hexamethylenediamine wherein the adipicacid product is prepared in accordance with the present invention.

Adipic acid is useful in the production of polyamides, such as nylon 6,6and nylon 4,6. See, for example, U.S. Pat. No. 4,722,997, and Musser,“Adipic Acid” in Ullmann's Encyclopedia of Industrial Chemistry,Wiley-VCH, Weinheim, 2005. The hexamethylenediamine formed from anadipic acid product prepared in accordance with the present inventioncan likewise be further used for the preparation of polyamides such asnylon 6,6 and nylon 6,12. See, for example Kohan, Mestemacher,Pagilagan, Redmond, “Polyamides” in Ullmann's Encyclopedia of IndustrialChemistry, Wiley-VCH, Weinheim, 2005.

Accordingly, adipic acid and a polymer precursor derived from an adipicacid product (e.g., hexamethylenediamine) may be reacted to produce apolyamide, wherein the adipic acid product is prepared in accordancewith the present invention. Polymer precursor, as used herein, refers toa monomer which can be converted to a polymer (or copolymer) underappropriate polymerization conditions. In various embodiments, thepolyamide comprises nylon 6,6. In these embodiments, nylon 6,6 isproduced by reacting an adipic acid product with a polymer precursorderived from an adipic acid product, wherein the polymer precursorcomprises hexamethylenediamine. In these embodiments,hexamethylenediamine may be prepared by converting an adipic acidproduct to adiponitrile which then may be converted to hexamethylenediamine, wherein the adipic acid product is prepared in accordance withthe present invention.

In other embodiments, an adipic acid product is converted to caprolactamwherein the adipic acid product is prepared in accordance with thepresent invention. The caprolactam formed can be further used for thepreparation of polyamides by means generally known in the art.Specifically, caprolactam can be further used for the preparation ofnylon 6. See, for example Kohan, Mestemacher, Pagilagan, Redmond,“Polyamides” in Ullmann's Encyclopedia of Industrial Chemistry,Wiley-VCH, Weinheim, 2005.

In various embodiments, nylon 6 is produced by reacting caprolactamderived from an adipic acid product prepared in accordance with thepresent invention.

In other embodiments, adipic acid and a polymer precursor may be reactedto produce a polyester, wherein the adipic acid product is prepared inaccordance with the present invention.

In other embodiments, an adipic acid product is converted to1,6-hexanediol wherein the adipic acid product is prepared in accordancewith the present invention. 1,6-hexanediol is a valuable chemicalintermediate used in the production of polyesters and polyurethanes.Accordingly, in various embodiments, polyester may be prepared byreacting adipic acid and 1,6-hexandiol derived from an adipic acidproduct, prepared in accordance with the present invention.

In various embodiments a salt of adipic acid may be produce wherein theprocess comprises reacting adipic acid with hexamethylenediamine,thereby forming the salt, wherein adipic acid is prepared in accordancewith the present invention.

When introducing elements of the present invention or the preferredembodiments(s) thereof, the articles “a”, “an”, “the” and “said” areintended to mean that there are one or more of the elements. The terms“comprising”, “including” and “having” are intended to be inclusive andmean that there may be additional elements other than the listedelements.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As various changes could be made in the above compositions and processeswithout departing from the scope of the invention, it is intended thatall matter contained in the above description shall be interpreted asillustrative and not in a limiting sense.

Having described the invention in detail, it will be apparent thatmodifications and variations are possible without departing from thescope of the invention defined in the appended claims.

EXAMPLES

The following non-limiting examples are provided to further illustratethe present invention.

Reactions were conducted in 1 mL glass vials housed in a pressurizedvessel in accordance with the procedures described in the examplesbelow. Product yields were determined using mass spectrometry throughcomparison with calibration standards.

Preparation of M1/Silica Catalysts (M1=Rh, Pd, Pt)

2 g of dried 5 μm Silica Cariact (Fuji Silysia) was weighed into vials.Suitably concentrated M1 stock solutions (M1=Rh, Pd, Pt) were preparedfrom concentrated acidic stock solutions purchased from Heraeus (seeTable 1). For each M1, multiple additions of the dilute M1 stocksolution were added to the silica (silica pore volume=0.7 mL/g) until atotal volume of 1.4 ml was reached. After each addition, the mixtureswere agitated to impregnate the silica. Post impregnation, the M1/Silicamixtures were dried in a furnace at 120° C. for 12 hours, followed bycalcination at 500° C. for 3 hours. Upon cooling the catalysts werestored in a dessicator until used.

Preparation of Tetrahydrofuran-2,5-Dicarboxylic Acid (THFDCA)

A 100 mL pressure vessel with a glass liner and an impeller was chargedwith 1.87 g of furan-2,5-dicarboxylic acid, 0.5 g of 4% Pd/Silica and 40mL of acetic acid. The pressure vessel was purged 3 times with nitrogen,and 2 times with hydrogen. The vessel was then pressurized to 750 psighydrogen and heated to 140° C. for 3 hours. After cooling the vessel wasvented and the solids were separated by filtration. The acetic acidsolution was evaporated under vacuum to provide 1.68 g (88% yield) oftetrahydrofuran-2,5-dicarboxylic acid.

Tetrahydrofuran-2,5-Dicarboxilic Acid to Adipic Acid Reactions

M1/Silica catalysts were transferred to 1 mL glass vials within a96-well reactor insert (Symyx Solutions). Each vial within each arrayreceived a glass bead and 250 μL of 0.2 M THFDCA, 0.1 to 0.3 M of HBr(Sigma-Aldrich) in Acetic Acid (Sigma-Aldrich), or HI (Sigma-Aldrich).Upon solution addition, the arrays of vials were covered with a Teflonpin-hole sheet, a silicone pin-hole mat and steel gas diffusion plate(Symyx Solutions). The reactor insert was placed in a pressure vessel,pressurized and vented 3 times with nitrogen and 3 times with hydrogenbefore being pressurized with hydrogen to 710 psig, heated to 140° C. or160° C. and shaken for 3 hours. After 3 hours the reactors were cooled,vented and purged with nitrogen. 750 μl of water was then added to eachvial. Following the water addition, the arrays were covered and shakento ensure adequate mixing. Subsequently, the covered arrays were placedin a centrifuge to separate the catalyst particles. Each reactionsamples was then diluted 100-fold with water to generate a sample foranalysis by mass spectrometry. The results are presented in Table 1.

TABLE 1 Halide Catalyst Adipic Example M1 Halide Concentration TempAmount Acid Yield Number Catalyst (wt. % M1/Support) Precursor Source(M) (° C.) (mg) (%) 1 5% Pd/Silica 5 μm Cariact Pd(NO₃)₂ HI 0.2 160 8 992 5% Rh/Silica 5 μm Cariact Rh(NO₃)₃ HI 0.2 160 8 91 3 5% Pd/Silica 5 μmCariact Pd(NO₃)₂ HI 0.2 140 8 70 4 5% Rh/Silica 5 μm Cariact Rh(NO₃)₃ HI0.2 140 8 68 5 5% Pd/Silica 5 μm Cariact Pd(NO₃)₂ HI 0.1 160 8 49 6 5%Rh/Silica 5 μm Cariact Rh(NO₃)₃ HI 0.1 160 8 33

What is claimed is:
 1. A process for preparing adipic acid comprisingreacting a tetrahydrofuranic substrate comprisingtetrahydrofuran-2,5-dicarboxylic acid with hydrogen, in the presence ofa hydrodeoxygenation catalyst, a solvent and a source of halogen, toconvert at least a portion of the tetrahydrofuran-2,5-dicarboxylic acidto adipic acid.
 2. The process as set forth in claim 1 wherein thesource of halogen comprises hydrogen bromide or hydrogen iodide.
 3. Theprocess as set forth in claim 1 further comprising reacting a furanicsubstrate comprising furan-2,5-dicarboxylic acid with hydrogen, in thepresence of a hydrogenation catalyst and a solvent, but in the absenceof an added source of halogen to produce the tetrahydrofuranic substratecomprising tetrahydrofuran-2,5-dicaboxylic acid.
 4. The process as setforth in claim 2 further comprising reacting a furanic substratecomprising furan-2,5-dicarboxylic acid with hydrogen, in the presence ofa hydrogenation catalyst and acetic acid, but in the absence of an addedsource of halogen to produce the tetrahydrofuranic substrate comprisingtetrahydrofuran-2,5-dicaboxylic acid.
 5. The process as set forth inclaim 1 wherein the solvent comprises a weak carboxylic acid.
 6. Theprocess as set forth in claim 1 wherein at least a portion of thetetrahydrofuranic substrate is derived from a carbohydrate source. 7.The process as set forth in claim 1 wherein the hydrodeoxygenationcatalyst comprises a heterogeneous catalyst.
 8. The process as set forthin claim 7 wherein the hydrodeoxygenation catalyst comprises at leastone d-block metal at a surface of a support.
 9. The process as set forthin claim 8 wherein the d-block metal is selected from the groupconsisting of Ru, Rh, Pd, Pt, and combinations thereof.
 10. The processas set forth in claim 1 wherein the hydrodeoxygenation catalystcomprises a first metal and a second metal, wherein the first metal isselected from the group consisting of Ru, Rh, Pd and Pt and the secondmetal is selected from the group consisting of Mo, Ru, Rh, Pd, Ir, Pt,and Au, and wherein the second metal is not the same as the first metal.11. The process as set forth in claim 10 wherein the hydrodeoxygenationcatalyst support comprises a material selected from the group consistingof carbon, silica, zirconia, and titania.
 12. The process as set forthin claim 3 wherein the source of halogen comprises hydrogen bromide orhydrogen iodide.
 13. The process as set forth in claim 1 wherein themolar ratio of the source of halogen to the tetrahydrofuranic substrateis equal to or less than about
 1. 14. The process as set forth in claim1 wherein the reaction mixture is maintained at a temperature of atleast about 100° C.
 15. The process as set forth in claim 3 wherein thetemperature of the hydrogenation reaction mixture is from about 60° C.to about 200° C.
 16. The process as set forth in claim 15 wherein thehydrodeoxygenation reaction is conducted under a partial pressure ofhydrogen ranging from about 25 psia (172 kPa) to about 2500 psia (17237kPa).
 17. The process as set forth in claim 3 wherein at least a portionof the furanic substrate is derived from a carbohydrate source.
 18. Theprocess as set forth in claim 3 wherein the hydrogenation catalystcomprises a heterogeneous catalyst.
 19. The process as set forth inclaim 18 wherein the hydrogenation catalyst comprises at least oned-block metal at a surface of a support.
 20. The process as set forth inclaim 19 wherein the d-block metal is selected from the group consistingof Ru, Rh, Pd, Pt, Ni, Co, Fe and combinations thereof.
 21. The processas set forth in claim 3 wherein the hydrogenation catalyst comprises afirst metal and a second metal, wherein the first metal is selected fromthe group consisting of Ru, Rh, Pd, Pt, Ni, Co and Fe, and the secondmetal is selected from the group consisting of Mo, Ru, Rh, Pd, Ir, Pt,and Au, and wherein the second metal is not the same as the first metal.22. The process a set forth in claim 20 wherein the hydrogenationcatalyst support comprises a material selected from the group consistingof carbon, zirconia, zeolite and silica.
 23. The process of in claim 3wherein the hydrogenation catalyst and the hydrodeoxygenation catalystare the same.
 24. The process of claim 3 wherein the hydrogenationreaction and the hydrodeoxygenation reaction are carried out indifferent reactors.
 25. The process of claim 3 wherein the hydrogenationreaction and the hydrodeoxygenation reaction are carried out in the samereactor.
 26. The process of claim 1 wherein the reaction temperature isat least about 140° C.
 27. The process of claim 1 wherein the yield ofadipic acid is at least about 90%.
 28. The process of claim 2 whereinadipic acid is produced at a yield of at least about 90%.
 29. Theprocess of claim 28 wherein the reaction temperature is at least about140° C.